JPH11163889A - Atm exchange - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce communication cost by providing an ATM exchange with a bypass selection device so as to select a path. SOLUTION: An ATM exchange provided with a bypass selection device IO has a usual path 1x, a bypass 1y and a cell output changeover section 13 and a path is switched by means of a software by changing a routing bit. Since the path is switched in a short time between the usual path 1x and the bypass 1y, probability of aborted cells to occur is decreased. Furthermore, additional devices required to select the usual path 1x and the bypass 1y is minimized. As a result, congestion of the communication network is prevented and the communication cost is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ATM (Asynchronous Transfer Mode) exchange provided with a detour path selecting device.

[0002]

2. Description of the Related Art With the development of multimedia, images,
There is a demand for a communication network that can support various media such as voice and data. In order to process these various and diverse media in a unified and uniform manner, AT
The development of the M communication network is expected. In the ATM communication, transfer information is cut into a fixed length, a cell to which a header having destination information and control information is added is formed, and this cell is transmitted as one unit. The originating exchange selects a transmission path for actually transmitting cells from a plurality of paths to the destination station. This transmission path is required to maintain good transmission quality. As one technique for maintaining transmission quality, for example, Japanese Patent Application Laid-Open No. 8-51440 can be cited.

In this technique, in addition to one transmission path from a transmitting station to a receiving station, another transmission path is selected. At the same time, the copied cells having the same contents are transmitted to the plurality of transmission paths. When a large number of cells received via one path are discarded due to a failure or the like, normal cells are received from the other transmission path to maintain quality.

[0004]

However, the above-mentioned technology has the following problems to be solved. 1. Since a plurality of routes are set and a duplicated cell is transmitted from the source station to the destination station, communication costs are increased. 2. There may be a time difference between the duplicated cells that have passed through the two transmission paths when they arrive at the destination station. At that time, a synchronous circuit and a circuit for absorbing a time difference were required in the transmission path. 3. Even if two transmission paths are selected, transmission quality cannot be maintained if a failure occurs in both transmission paths. On the other hand, if three or more transmission paths are used, the communication cost is further increased.

[0005]

The present invention adopts the following constitution in order to solve the above points. <Configuration 1> A normal path for transmitting cells during normal operation and a bypass path not used during normal operation are set,
An ATM network management unit that controls the entire ATM switch;
A cell output switching unit for switching path selection so that, when an abnormality occurs in the normal path under control of the TM network management unit, a cell to be transmitted to the normal path is transmitted to a detour path. Characteristic ATM switch.

<Structure 2> In the structure described in Structure 1,
An ATM exchange comprising a cell header conversion unit for adding path switching information to routing information of a cell header.

<Structure 3> In the structure described in Structure 2,
The path information to be added to the routing information of the cell to be transmitted to the normal path and the path information to be added to the routing information of the cell to be transmitted to the detour path are simultaneously stored in separate memory addresses in the conversion information memory. RB for selecting one of these memory addresses
An ATM exchange comprising a rewriting unit.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. FIG. 1 is a block diagram of a bypass route selection device according to a first embodiment. Before describing FIG. 1, in order to facilitate understanding of the detour route selection device,
First, an outline of an ATM exchange and its operation will be described with reference to the drawings. The detour route selection device is a component of the ATM switch.

FIG. 2 is an explanatory diagram of an ATM exchange. As shown in the figure, the ATM switch 30 includes an incoming line corresponding unit 31, a communication path 32, an outgoing line corresponding unit 33, and an ATM network management unit 20.
Is provided. The incoming line corresponding unit 31 accommodates a transmission line connected to the terminal device 14. Also, the outgoing line correspondence unit 33
Accommodates a transmission path connected to the destination terminal 15.

The incoming line correspondence unit 31 is a unit that converts a cell header transmitted from the terminal device 14 into routing information of a switch circuit in the communication path 32, and has an incoming line table 34. The detour route selection device according to the specific example corresponds to this part. Here, the routing is an operation of selecting a route. The communication path 32 is a part that performs switching based on the routing information and controls transmission of cells to the corresponding path.

The outgoing line corresponding section 33 is a section for converting header information of a cell transmitted from the communication path 32 into outgoing line information for going to the destination station. ATM network management unit 20
Is a section for controlling the operation of each section of the ATM exchange as described above, and for managing the entire ATM network in cooperation with other exchanges.

Next, an outline of the operation of the ATM exchange will be described. The description will be made according to the numbers (1) to (5) in the figure. (1) The cell transmitted from the terminal device 14 to the destination terminal 15 arrives at the incoming line corresponding unit 31 via the incoming line. (2) Under the control of the ATM network management unit 20, the incoming line correspondence unit 31 stores the routing information (m) of the switch circuit stored in the address a of the incoming line table 34 based on the header a of the incoming cell. Then, the reference information (X) required by the outgoing line corresponding unit is read and the header is converted.

(3) The cell in which the above two pieces of information have been read and the header has been converted proceeds to the communication path 32. (4) The communication path reads the routing information (m) of the switch circuit from the header. This routing information (m)
The switch of the communication path 32 is turned on / off based on the above to form a path in the communication path 32. The cells that passed this route
The process proceeds to the outgoing line corresponding section 33 of the target outgoing line. (5) The outgoing line corresponding unit 33 reads the reference information (X) from the header.
Is read, and the route information b toward the called station stored at the address X of the outgoing line table 35 is read. This b
To convert the header again. Thereafter, the cell is transmitted to the receiving station based on this b. Since the outline of the ATM exchange has been described above, returning to FIG. 1 again, the alternate route selection device according to the first embodiment will be described.

<Configuration of Specific Example 1> As shown in FIG. 1, the detour path selecting apparatus 10 according to the specific example 1 includes a cell header conversion unit 11
, Conversion information memory 12 and cell output switching unit 13
And a normal route 1x and a detour route 1y. The cell header conversion unit 11 generates a memory address a from a cell header received from the terminal device 14 via the incoming line 1z. Next, the data at the address a in the conversion information memory 12 is read based on a. Further, it is a section for reading the switching information (m) of the switch circuit and the reference information (X) required at the outgoing line corresponding section stored at the address a and converting the header. The conversion information memory 12 is a memory for storing the switching information (m) of the switch circuit and the reference information (X) required by the outgoing line correspondence unit, which are written by the ATM network management unit 20 controlling the ATM exchange. is there. The information stored in this memory is stored in the ATM network management unit 20.
Must be stored in advance.

Therefore, at the time of activation, the ATM network management unit 20 (FIG. 1) is activated first and stores data in the conversion information memory 12 via the bus 10a. After that, the cell header conversion unit 11 needs to be activated. Further, during the operation of the cell header conversion unit 11, data may need to be rewritten. At that time, it is necessary to prepare a conversion information memory 12 having a two-plane configuration in advance, rewrite the non-linked plane, and switch the plane.

The cell output switching unit 13 is a switch for distributing cells to the normal route 1x and the detour route 1y under the control of the ATM network management unit 20 with reference to the cell header. Both the normal route 1x and the detour route 1y are connected to a communication path (FIG. 2) in the ATM exchange. The normal path 1x is exactly the same as that used in a normal ATM exchange. The detour route 1y is an unused route during normal operation, and is a backup route set for the time of occurrence of some abnormality. It is preferable that the backup path is not used normally, and is a highly reliable backup path that is normally operated even if a failure occurs in the normal path. The above normal route 1
Selection of x and the detour path 1y is performed using one or several bits in the cell header.

<Operation of Embodiment 1> FIG. 3 is an explanatory diagram of the operation of Embodiment 1. Hereinafter, the operation of the bypass route selection device according to the first embodiment will be described with reference to the drawings. A cell transmitted from the terminal device 14 to the destination terminal 15 (FIG. 2) arrives at the detour route selecting device 10 through the incoming line. The cell header conversion unit 11 calculates the memory address a from the cell header.
Generate Further, the conversion information memory 1 is connected via the bus 10b.
2 instructs data read of the generated memory address a, and reads the data via the bus 10c. The normal path 1x and the detour path 1y are designated using one bit or several bits of this data. This bit is defined as routing (hereinafter referred to as RB).

When RB = 0, the normal route 1x
It is assumed that the alternative route 1y is selected when = 1. The cell header conversion unit 11 reads the information b1 (RB = 0) and converts the cell header. The cell whose cell header has been converted is
The process proceeds to the cell output switching unit 13 through the bus 10d. The cell output switching unit 13 reads RB = 0 in the cell header and sends this cell to the normal route 1x. Hereinafter, the call arrives at the called station following the normal route. Assume that RB = 1. This state is a state where some abnormality has occurred in the normal route 1x.

The ATM network management unit 20 detects some abnormality in the normal route 1x and changes the RB in the address a of the conversion information memory 12 to 1. As described above, rewriting during operation is possible by preparing the conversion information memory 12 having a two-plane configuration in advance.
When RB = 1, the cell output switching unit 13 reads RB = 1 in the cell header and sends this cell to the bypass route 1y. The call arrives at the receiving station without dropping through the bypass route 1y. Further, based on the control of the ATM network management unit 20, when the cell switching unit 13 is RB = 1, the normal route 1x
Alternatively, when RB = 0, the switching to the detour path 1y can be changed. With this change, the conversion information memory 1
It is also possible to switch the route without rewriting 2.

<Effects of Specific Example 1> The ATM switch provided with the detour path selecting device 10 according to the specific example 1 is capable of performing the detour path 1y.
The switching between the normal path and the normal path is performed in a software manner by changing the routing bit, and the following effects are obtained. 1. Since the route switching between the normal route 1x and the detour route 1y can be executed in a short time, the probability of occurrence of a cell drop is reduced. 2. Additional facilities required for switching the route between the normal route 1x and the detour route 1y can be minimized.

3. As a result, it helps to prevent congestion in the communication network, and further reduces the communication cost. 4. It is no longer necessary to flow cells through the normal route 1x and the detour route 1y at the same time. Therefore, since it is not necessary to consider the time difference between the two paths, a synchronous circuit and a line capacitance for absorbing the time difference are not required.

<Structure of Embodiment 2> FIG. 4 is a block diagram of a high-speed bypass route selecting apparatus according to Embodiment 2. The high-speed bypass route selection device 40 includes an RB rewrite unit 16, a cell header conversion unit 11, a conversion information memory 12, a cell output switching unit 13, a normal route 1x, and a bypass route 1y. The RB rewriting unit 16 is connected between the terminal device 14 and the cell header conversion unit 11, and is a unit that changes a routing bit (RB) in an electronic circuit in a hardware manner under the control of the ATM network management unit 20. Other configurations are the same as those of the first embodiment.

<Operation of Embodiment 2> FIG. 5 is an explanatory diagram of the operation of Embodiment 2. The cell a transmitted from the terminal device 14 to the destination terminal 15 (FIG. 2) arrives at the high-speed bypass route selection device 40 via the incoming line. Cell a is an RB rewriting unit 1 located at the input end of the high-speed detour route selection device 40.
Proceed to 6. It is assumed that the RB rewriting unit 16 rewrites the RB of the cell a to 0 based on the control of the ATM network management unit 20. This cell is designated as a1. This cell is a cell that travels the normal route 1x. Similarly, when RB = 1 is rewritten, it is set to a2. This cell is a cell that proceeds on the detour route 1y.

In FIG. 5, the cell a becomes a1 and the process proceeds to the cell header converter 11. The cell header conversion unit 11 generates a memory address a1 from the cell header. Bus 10b
And instructs the conversion information memory 12 to read out the data of the generated memory address a1 via the bus 10c. The normal path 1x is selected using one bit or several bits of this data. Cell header conversion unit 11
Reads the information b1 (RB = 0) and converts the cell header. The cell whose cell header has been converted proceeds to the cell output switching unit 13 through the bus 10d. The cell output switching unit 13 reads RB = 0 in the cell header and sends this cell to the normal route 1x. Hereinafter, the call arrives at the called station following the normal route.

Similarly, it is assumed that cell a has become a2 and has proceeded to cell header converter 11. The cell header conversion unit 11 generates a memory address a2 from the cell header. In the conversion information memory 12 via the bus 10b,
The data read of the generated memory address a2 is instructed and read via the bus 10c. The bypass route 1y is selected using one bit or several bits of this data.
The cell header conversion unit 11 reads the information b2 (RB = 1) and converts the cell header. The cell whose cell header has been converted proceeds to the cell output switching unit 13 via the bus 10d. The cell output switching unit 13 calculates the cell header RB =
After reading 0, this cell is transmitted to the bypass route 1y. Hereinafter, the call arrives at the called station along the detour route.

Hereinafter, differences from the first embodiment will be described. In the specific example 1, the terminal device 14 sends the destination terminal 15
The conversion information memory 12 allocates one memory address a on the memory map for the cell a transmitted toward (FIG. 2). The distribution of RB = 0 and RB = 1 is performed in software by the ATM network management unit 20 by rewriting the data of the one memory address a. On the other hand, in the specific example 2, 2
Addresses a1 and a2 are assigned. Information of RB = 0 and RB = 1 is stored in the two addresses a1 and a2, respectively. The RB = 0 and RB = 1 are distributed by the RB rewriting unit 16 by hardware.

<Effect of Specific Example 2> The ATM switch provided with the high-speed detour path selecting device 40 according to the specific example 2 has two items in the memory map of the conversion information memory 12 for the normal route 1x and the detour route 1y. The following effects are obtained by allocating a memory address and performing this read switching by the RB rewriting unit 16. 1. Normal route 1x and detour route 1
By simultaneously storing the information of y, the normal route 1x
And the route switching to the detour route 1y can be performed in a shorter time. 2. The cell is easily copied, and the normal route 1x and the detour route 1y can be used at the same time. Therefore, maintenance of transmission quality has become much easier.

[Brief description of the drawings]

FIG. 1 is a block diagram of a detour path selection device according to a specific example 1.

FIG. 2 is an explanatory diagram of an ATM exchange.

FIG. 3 is an operation explanatory diagram of a specific example 1.

FIG. 4 is a block diagram of a high-speed detour route selection device according to a specific example 2.

FIG. 5 is an operation explanatory diagram of a specific example 2.

[Description of Signs] 10 detour path selection device 11 cell header conversion unit 12 conversion information memory 13 cell output switching unit 14 terminal device 20 ATM network management unit

Claims (3)

[Claims] 1. A normal path for transmitting cells during a normal operation and a detour path not used during a normal operation are set, and an ATM network management unit for controlling the entire ATM exchange is controlled by the control of the ATM network management unit. An ATM exchange, comprising: a cell output switching unit for switching path selection so that a cell to be transmitted to the normal path is transmitted to a detour path when an abnormality occurs in the normal path. 2. The ATM switch according to claim 1, further comprising a cell header conversion unit for adding path switching information to routing information of a cell header. 3. The method according to claim 2, wherein the path information to be added to the routing information of the cell to be transmitted to the normal path and the path information to be added to the routing information of the cell to be transmitted to the detour path are converted. The information is stored simultaneously in separate memory addresses in the information memory, and R is used to select one of these memory addresses.
An ATM exchange comprising a B rewriting unit.